City of El Mirage achieves significant reliability gains with Qdos® chemical metering pumps

The City of El Mirage, Arizona has significantly improved reliability and reduced maintenance at its water and wastewater treatment facilities since replacing diaphragm pumps with 13 Qdos^® 20 peristaltic chemical metering pumps.

The Qdos 20 pumps, which were installed at remote well sites and a wastewater reclamation facility, have also contributed to the reduction of chemical costs and flushing requirements.

Before adopting Qdos technology, El Mirage relied on a mix of diaphragm pumps that struggled to deliver consistent chemical dosing. These pumps were prone to breakdowns, caused overdosing issues, and posed safety concerns during maintenance. They required the City of El Mirage water treatment team (City) to maintain a large spare parts inventory, including a $20,000 chlorine parts budget.

By contrast, Qdos pumps provide accurate, repeatable flow rates and long maintenance intervals, reducing downtime and lowering total cost of ownership.

The Qdos 20 pumps offer simple drop-in installation, which eliminates ancillary equipment such as back-pressure valves, pulsation dampeners, degassing valves, foot valves, strainers, or float switches—simplifying setup and cutting costs. Pump maintenance is reduced with the single, no-tools, component replacement feature.

The Qdos range of pumps, including H-FLO for higher flow rates, is designed for applications up to 158.5 USGPH (600 L/h) in a variety of materials for compatibility at up to 102 PSI (7 bar). Qdos pumps are ideal for most chemistries, especially those that are viscous, abrasive or off-gas. Qdos can handle gaseous fluids such as sodium hypochlorite, as well as dosing viscous polymers as part of wastewater treatment.

Since switching to ten Qdos 20 pumps at nine remote well sites in 2019 and 2020, the City has experienced no pump or pumphead failures. The pumps have delivered long service life in a variety of harsh climates in the Arizona desert. No maintenance has been required other than changing the pumphead once a year. The repeatable metering and dosing throughout the pumphead life has eliminated overdosing issues experienced with the previously used diaphragm pumps.

Chemical savings

Scott Ketchmark, Water/Wastewater  Operations Superintendent at City of El Mirage, said that the City set a distribution chlorine target residual at 1.0 parts per million (ppm) in 2019. The residual annual average over four years (480 samples per year for a total of 1,920 tests) has met the 1.0 ppm target exactly.

Scott Ketchmark said: “This has eliminated nearly all resident chlorine, smell, or taste complaints. We have been able to reduce the amount of sodium hypochlorite purchases each year because of higher accuracy metering, which has also reduced the distribution system flushing requirement.”

In addition, the chlorine pump parts cost plummeted from $20,000 a year to less than $3,000 per year, with no change in flow over time.

At the El Mirage Wastewater Reclamation Facility (WRF), domestic and commercial wastewater flows by gravity or is pumped to the WRF from two lift stations throughout the system. After several treatment processes, polished filter effluent is discharged into a clear well, which provides 1.5 additional hours of contact time needed for disinfection. A sodium hypochlorite solution is injected into the filter effluent. During the disinfection process, the treated wastewater flows by gravity through chlorine contact piping and then into the reuse pump station, which is the final step in the treatment process.

Two Qdos 20 units are being used in this disinfection step. Since switching to the pumps from WMFTS, operators have experienced no pump or pumphead failures. They find the reliability to be a huge advantage, with no maintenance required other than switching out the pumphead.

Another Qdos 20 pump is used for the WRF’s activated sludge dewatering process. The Qdos 20 pump provides a low shear effect on the coagulant polymer. In concentrated form the polymer is like a coiled spring: if uncoiled too much (high shear), the polymer becomes fragile and can break under high sheer conditions. High-shear conditions can impact the efficiency of the process ultimately costing more money.

Similar to pumps at the well sites, the repeatable metering and dosing throughout the pumphead life eliminated chemical overdosing.

Learn more about Qdos chemical metering pumps